Vegetated Open Channels

Purpose/Function:

Runoff passes through either vegetation in the channel, subsoil matrix and/or is infiltrated into the underlying soils.

Initiation protocol:

Site assessment for buried infrastructure and other utilities must be undertaken.

Public acceptance:

The public likely does not recognize this practice as it is relatively benign in appearance.

Implementation Factors (level of difficulty):

Moderate.

Funding Sources / Options:

This practice is typically funded by developers during construction.

Costs:

Costs estimated as $ per impervious acre treated.

Cost Estimates

EPA

King & Hagan

Average

Initial

$762

$6,500

$3,631

Annual

$507

$128

$317.50

Lifespan (yrs)

20

20

20

Annualized

$545.10

$453

$499.05

Notes: King & Hagan figures are expressed in units of “impervious acres treated”. This provides a unit of comparison that is more uniform than “acres treated,” which assumes a proportion of impervious to pervious coverage. EPA figures have been converted.

Load Reduction Efficiency:

Total Nitrogen removed per impervious acre treated per year

Low

2.67 lbs.

Medium

3.06 lbs.

High

6.28 lbs.

Cost per pound removed = between $79 and $187

Total Phosphorous removed per impervious acre treated per year

Low

0.10 lbs.

Medium

0.17 lbs.

High

0.49 lbs.

Cost per pound removed = between $1,024 and $5,045

Total Suspended Solids removed per impervious acre treated per year

Low

44 lbs.

Medium

84 lbs.

High

534 lbs.

Cost per pound removed = between $0.93 and $11.24

Operation & Maintenance:

These grasses are sod-forming and can withstand frequent inundation and are ideal for the swale or grass channel environment. Most are salt-tolerant, as well.

Planning Questions to Consider:

If this BMP is likely to receive excessive amounts of deicing salt, salt tolerant species should be used.